The left has used name calling and abuse of those who did not share their views to silence debate which was a great own goal since it drove dissenting opinion underground. Those with rational, reasonable and moderate views learned to keep quiet to avoid being labelled a racist, a bigot or a fascist.
The result of this was that swathes of decent, ordinary but silent people came out on election days and voted for a Conservative government and then for Brexit to the astonishment of those who silenced their neighbours but forgot that those they abused had a vote in a secret ballot.
One of the greatest faults of the left was to deliberately assume the irrational view that if someone disagreed with one, single tenet of an opposing opinion they were to be lumped in with the far right. Thus it was that, if Islam's inherent misogyny was qeven mildly questioned, the interlocutor was accused of being racist and of hating everyone different from them, an absurd and insulting assumption.
The consequence of this was seen in the Rotherham, Rochdale child-raping scandals where abuse continued for years for fear that local authorities could be accused of being racists for identifying the actual perpetrators of monstrous crimes.
People did not even feel they could speak out aginst this outrage so they voted instead.
As here so in America with the shock election of Donald Trump, the left created the right.